tire

Abstract

To provide a tire improved in grip performance.SOLUTION: A tire comprises a tread. The tread is composed of a rubber composition containing a rubber component. The tire has a ratio (G / WL) of tire weight G (kg) to maximum load capacity WL (kg) of 0.0150 or less. When an average value of coefficients of static friction of the rubber composition measured five times at a ground contact pressure of 0.30 MPa and at a measurement temperature of 25°C on a road surface according to ISO15222 is represented by μ, G / WL and μ satisfy a following expression (1): (G / WL) / μ≤0.0214 ... (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] For tires fitted to automobiles, maintaining grip between the tread and the road surface is crucial during driving, braking, and cornering. Conventionally, various methods have been considered to improve grip performance. For example, Patent Document 1 describes a pneumatic tire equipped with a tread rubber that enhances grip performance by using fine zinc oxide particles. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-285524 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a tire with improved grip performance. [Means for solving the problem]

[0005] In other words, the present invention relates to the following tires. A tire having a tread, The tread is made of a rubber composition containing rubber components, The ratio of the tire weight G (kg) to the tire's maximum load capacity WL (kg) (G / WL) is 0.0150 or less. A tire in which G / WL and μ satisfy the following equation (1), when the average value of the static friction coefficient of the rubber composition measured five times on a road surface conforming to ISO 15222 at a ground pressure of 0.30 MPa and a measurement temperature of 25°C is μ. (G / WL) / μ≦0.0214 (1) [Effects of the Invention]

[0006] According to the present invention, a tire with improved grip performance can be provided. In the present specification, grip performance means dry grip performance, unless it is explicitly stated that the grip performance is under wet conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] [Figure 1] FIG. 1 is a diagram showing a tire cross-sectional width Wt, a tire cross-sectional height Ht, and a tire outer diameter Dt in a cross-section of a tire. [Figure 2] FIG. 2 is a diagram schematically illustrating a tread contact patch in a tire according to an embodiment of the present invention. The enclosed region in the figure is the tread contact patch. [Figure 3] FIG. 3 is a diagram showing a tread pattern of a tire according to an embodiment of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0008] A tire according to an embodiment of the present invention is a tire provided with a tread, the tread is formed of a rubber composition containing a rubber component, the ratio (G / WL) of tire weight G (kg) to maximum load capacity WL (kg) of the tire is 0.0150 or less, and when μ is the average value of the static friction coefficients of the rubber composition measured 5 times on a road surface conforming to ISO15222 at a contact pressure of 0.30 MPa and a measurement temperature of 25° C., the tire satisfies the following formula (1) with G / WL and μ. (G / WL) / μ≦0.0214 (1)

[0009] While not intending to be bound by theory, the following mechanism is conceivable as the mechanism by which grip performance can be improved in the present invention. That is, (1) a tire with reduced G / WL is a tire having a relatively smaller tire weight relative to the maximum load capacity, and when such a tire is used, the vehicle weight, particularly the unsprung weight, is reduced. Therefore, the ratio of the tire's grip force to the vehicle weight is improved, and it can be expected that the grip force of the vehicle as a whole is relatively improved. Furthermore, (2) by setting G / WL to a predetermined value or less in terms of the ratio to the coefficient of static friction (μ), G / WL is prevented from becoming excessively large and the coefficient of static friction is prevented from becoming excessively small, since the two parameters constrain each other. Accordingly, an improvement in grip force can also be expected from this. It is considered that the improvement in grip performance achieved in the present invention is attained through the synergistic effect of these factors.

[0010] The value of G / WL is preferably 0.0140 or less.

[0011] This is considered to contribute to improving the grip performance of the tire.

[0012] The value of μ is preferably 0.65 or more.

[0013] This is considered to contribute to improving the grip performance of the tire.

[0014] The value on the right-hand side of formula (1) is preferably 0.0202.

[0015] It is considered that, since the two parameters constrain each other such that G / WL does not become excessively large and the coefficient of static friction does not become excessively small, this contributes to improving grip performance.

[0016] The rubber component preferably includes an isoprene-based rubber.

[0017] Inclusion of an isoprene-based rubber increases the adhesiveness of the rubber surface, and therefore this is considered to contribute to improving the coefficient of static friction.

[0018] The rubber composition preferably contains a resin component.

[0019] This is thought to contribute to improving the coefficient of static friction.

[0020] The loss tangent (30°C tanδ) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, is preferably greater than 0.17.

[0021] By setting the tanδ in the room temperature range to a predetermined value or higher, it is believed that this will contribute to improving grip performance in that temperature range.

[0022] The complex modulus of elasticity (30°C E*) (MPa) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, is preferably less than 9.5.

[0023] By keeping the E* value below a predetermined value in the ambient temperature range, the ability to follow road surface irregularities is improved, and as the amount of rubber deformation increases, energy loss increases, which is thought to contribute to improved grip performance.

[0024] Preferably, the product of the loss tangent (30°C tanδ) of the rubber composition measured under conditions of a temperature of 30°C, initial strain of 5%, dynamic strain of 1%, and frequency of 10Hz, and the loss tangent (0°C tanδ) of the rubber composition measured under conditions of a temperature of 0°C, initial strain of 10%, dynamic strain of 2.5%, and frequency of 10Hz, is greater than 0.11.

[0025] By setting the tanδ in the low-temperature range to the room-temperature range to a predetermined value or higher, it is believed that this will contribute to improving grip performance in that temperature range.

[0026] The rubber composition contains a resin component, and it is preferable that the amount of the resin component is more than 10 parts by mass per 100 parts by mass of the rubber component.

[0027] This is thought to contribute to improving the coefficient of static friction.

[0028] The rubber composition contains a resin component, and it is preferable that the resin component contains at least one selected from the group consisting of C5C9 petroleum resins, terpene resins, and rosin resins.

[0029] This is thought to contribute to improving the coefficient of static friction.

[0030] The rubber composition comprises a filler, the filler comprises carbon black and silica, and preferably the mass ratio of silica to carbon black is greater than 1.0.

[0031] By incorporating more silica than the specified amount into the carbon black mixture, the ability to follow the road surface is improved, which is thought to contribute to an improvement in the static friction coefficient.

[0032] Preferably, the tread surface of the tread has one or more circumferential grooves extending continuously in the tire circumferential direction and a land area partitioned by the circumferential grooves, the land area has transverse grooves extending in the tire width direction, and the transverse grooves have a portion in a cross section perpendicular to the tire diameter direction in which the groove width is wider than the groove width on the tread surface.

[0033] Even as the tread wears down, the groove area of ​​the lateral grooves expands, which is thought to improve drainage performance and thus contribute to improved grip performance.

[0034] The tread surface of the tread has one or more circumferential grooves extending continuously in the circumferential direction of the tire, and a land area partitioned by the circumferential grooves, and it is preferable that the ratio of the area of ​​the circumferential grooves to the area of ​​the tread contact surface is greater than 19% and less than 32%.

[0035] By making the groove area of ​​the circumferential grooves greater than a predetermined value, drainage can be ensured, which is expected to contribute to improved grip performance.

[0036] The tread surface of the tread has three or more circumferential grooves extending continuously in the circumferential direction of the tire, and a land area partitioned by the circumferential grooves, wherein the circumferential grooves consist of a pair of outermost circumferential grooves at the outermost edge in the tire width direction and a center circumferential groove in the tire width direction from the pair of outermost circumferential grooves, the land area is partitioned into a shoulder land area outside the tire width direction from the outermost circumferential grooves and a center land area in the tire width direction from the outermost circumferential grooves, the shoulder land area has a shoulder lateral groove extending in the tire width direction, the center land area has a center lateral groove extending in the tire width direction, one end of the shoulder lateral groove opens to the tread contact edge and the other end opens to the outermost circumferential groove, one end of the center lateral groove opens to the outermost circumferential groove and the other end opens to the center circumferential groove, and preferably the shoulder lateral groove and the center lateral groove constitute a series of lateral grooves extending continuously from the tread contact edge toward the tire equator.

[0037] This configuration allows for efficient drainage from the center of the tire towards the tread contact edge, which is expected to contribute to improved grip performance.

[0038] <Definition> Unless otherwise specified, the "dimensions of each part of the tire" refer to the values ​​specified in the standard unloaded condition, when the tire is mounted on a standard rim and filled with the standard internal pressure.

[0039] "Tire weight G (kg)" is the weight of the tire alone, excluding the weight of the rim.

[0040] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standards, it refers to the rim with the smallest diameter and the narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage between the rim and tire.

[0041] "Regular internal pressure" refers to the air pressure specified for each tire in the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the maximum value listed under "INFLATION PRESSURE" for ETRTO. Similar to "regular rim," refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. For tires not specified in the standard, it refers to the regular internal pressure (but 250 kPa or higher) of another tire size (specified in the standard) that uses the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0042] "Regular load" refers to the load specified in the standards system, including the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are all regular loads, and as with the "regular rim" and "regular internal pressure" mentioned above, refer to JATMA, ETRTO, and TRA in that order and follow their respective standards.

[0043] The "maximum load capacity (WL) (kg)" is a value calculated using the following formulas (1) and (2), where Wt (mm) is the tire section width, Ht (mm) is the tire section height, and Dt (mm) is the tire outer diameter, as measured under normal conditions. V is the virtual volume of space occupied by the tire. The tire section width Wt is the maximum width between the outer surfaces of the sidewalls, excluding any patterns or letters on the tire sidewall. The tire section height Ht is the distance from the bottom of the bead to the outermost surface of the tread, and is half the difference between the tire outer diameter and the nominal rim diameter. Figure 1 shows the tire section width Wt, tire section height Ht, and tire outer diameter Dt. V = {(Dt / 2)} 2 -(Dt / 2-Ht) 2} × π × Wt ···(1) WL = 0.000011 × V + 100 ... (2)

[0044] The "tread contact area" refers to the surface where the tread makes contact with the ground when a tire is mounted on a standard rim, filled to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. For example, it can be obtained by applying ink to the tread surface and pressing it onto cardboard. The area of ​​the tread contact area is calculated by rotating the tire 72° in the circumferential direction, transferring the contact shape at five different points, obtaining the contact shape five times, and then taking the average value. Figure 2 schematically represents the tread contact area. The enclosed area in the figure is the tread contact area.

[0045] The "tread contact point" is the outermost point of contact with the ground when a tire is mounted on a standard rim, filled to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load.

[0046] A "circumferential groove" is a groove that extends continuously in the circumferential direction of the tire on the tread surface. The pair of circumferential grooves located on the outermost side in the tire width direction are called the outermost circumferential grooves, and the circumferential grooves located inward from the pair of outermost circumferential grooves in the tire width direction are called the center circumferential grooves.

[0047] The "land area" refers to the region of the tread surface demarcated by circumferential grooves. The land area located outside the outermost circumferential groove in the tire width direction is called the shoulder land area, and the land area located inside the outermost circumferential groove in the tire width direction is called the center land area.

[0048] A "lateral groove" refers to a groove that extends in the width direction of the tire on the land portion. Lateral grooves include lateral grooves where the groove width is wider than the groove width on the tread surface in a cross section perpendicular to the tire diameter (widened lateral grooves), lateral grooves located on the shoulder land portion (shoulder lateral grooves), and lateral grooves located on the center land portion (center lateral grooves). In this specification, lateral grooves include not only grooves with a width of 2 mm or more on the tread surface, but also grooves with a width of less than 2 mm, which are usually called sipes.

[0049] <Measurement method> The "static friction coefficient μ" is the maximum static friction coefficient of rubber. It is the average value obtained by measuring the maximum static friction coefficient five times using a TL501 SLIPMETER (manufactured by Trinity Lab Co., Ltd.) on a road surface compliant with ISO 15222, under conditions of a contact pressure of 0.30 MPa and a measurement temperature of 25°C, with the pushing speed being a speed at which the tire moves from θ=0° (vertical position) to 60° in 3 seconds. The sample for measuring the static friction coefficient is a vulcanized rubber composition measuring 27 mm in length, 25 mm in width, and 8 mm in thickness. When preparing the sample by cutting it from a tire, cut it from the tire tread surface so that the longer side is in the circumferential direction of the tire and the thickness is in the radial direction of the tire.

[0050] "tanδ at 30°C (30°C tanδ)" is the loss tangent measured in extension mode using a dynamic viscoelasticity measuring instrument (e.g., GABO's Iplexer series) under the conditions of 30°C, initial strain of 5%, dynamic strain of 1%, and frequency of 10Hz. The sample for loss tangent measurement is a vulcanized rubber composition measuring 20mm in length, 4mm in width, and 1mm in thickness. When prepared by cutting from a tire, it is cut from the inside of the tire tread so that the longer side is in the circumferential direction of the tire and the thickness is in the radial direction of the tire.

[0051] The "complex modulus at 30°C (30°CE*)" is the complex modulus (MPa) measured in extension mode using a dynamic viscoelasticity analyzer (e.g., GABO's Iplexer series) under the conditions of 30°C, initial strain of 5%, dynamic strain of 1%, and frequency of 10Hz. The sample for complex modulus measurement is prepared in the same manner as for 30°C tanδ.

[0052] "Tanδ at 0°C (0°C tanδ)" is the loss loss tangent measured in extension mode using a dynamic viscoelasticity measuring instrument (e.g., GABO's Iplexer series) under the conditions of 0°C temperature, 10% initial strain, 2.5% dynamic strain, and 10 Hz frequency. The sample for 0°C tanδ measurement is prepared in the same manner as for 30°C tanδ.

[0053] "Styrene content" is, 1 It is calculated by 1H-NMR measurement.

[0054] The "vinyl bond amount (amount of 1,2-bonded butadiene units)" is calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017.

[0055] The "cis content (amount of cis-1,4-bonded butadiene units)" is calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017.

[0056] The "glass transition temperature (Tg)" is measured in accordance with JIS K 7121, using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan, by measuring while increasing the temperature at a heating rate of 10°C / min.

[0057] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series manufactured by Tosoh Corporation, with a differential refractometer as the detector and TSKGEL SUPERMALTIPORE HZ-M column manufactured by Tosoh Corporation) to a standard polystyrene equivalent.

[0058] The N2SA rating of carbon black is measured in accordance with JIS K 6217-2:2017.

[0059] The N2SA content of silica is measured by the BET method in accordance with ASTM D3037-93.

[0060] The "average primary particle diameter" can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles observed within the field of view, and averaging the results. For spherical particles, the diameter of the sphere is used as the particle diameter; for needle-shaped or rod-shaped particles, the shorter axis is used; and for irregularly shaped particles, the average of the shorter and longer axes is used. This method is applied to materials such as carbon black and silica.

[0061] The "softening point" can be defined as the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2001 is measured using a ring-type softening point measuring device.

[0062] "Plasticizer content" includes the amount of plasticizer in the rubber component stretched by the plasticizer. Similarly, "oil content" includes the amount of oil contained in the oil-stretched rubber.

[0063] [tire] The tire of the present invention will be described with reference to the drawings as appropriate. However, the following description is illustrative for explaining the present invention and is not intended to limit the technical scope of the present invention to this description alone.

[0064] (G / WL) The tire of the present invention has a ratio of tire weight G (kg) to maximum load capacity WL (kg) (G / WL) of 0.0150 or less. The value of G / WL is preferably 0.0145 or less, more preferably 0.0140 or less, even more preferably less than 0.0140, even more preferably less than 0.0135, and even more preferably 0.0131 or less. There is no particular limit on the lower limit, but it is usually around 0.0129.

[0065] (tread) The tire of the present invention is equipped with a tread. The tread is made of a rubber composition containing a rubber component.

[0066] The rubber composition has a loss tangent (30°C tanδ) measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, which is preferably greater than 0.17, more preferably greater than 0.20, even more preferably 0.21 or higher, even more preferably 0.22 or higher, even more preferably 0.23 or higher, and even more preferably 0.24 or higher.

[0067] The rubber composition has a complex modulus of elasticity (30°C E*) (MPa) measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, which is preferably less than 9.5, more preferably less than 9.0, even more preferably 8.9 or less, even more preferably less than 8.5, even more preferably less than 8.4, even more preferably 8.3 or less, even more preferably 8.2 or less, and even more preferably 8.1 or less.

[0068] The rubber composition has a product (30°C tanδ × 0°C tanδ) of 30°C tanδ and the loss loss tangent (0°C tanδ) of the rubber composition measured under the conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, and a frequency of 10Hz, which is preferably greater than 0.11, more preferably 0.12 or greater, even more preferably 0.13 or greater, and still more preferably 0.15 or greater.

[0069] (Formula (1)) The static friction coefficient of the rubber composition, measured five times on a road surface conforming to ISO 15222 at a ground pressure of 0.30 MPa and a measurement temperature of 25°C, satisfies the following equation (1), where μ is the average value of the five measurements: G / WL and μ. (G / WL) / μ≦0.0214 (1)

[0070] The value of μ is preferably 0.65 or higher, more preferably 0.70 or higher, even more preferably greater than 0.75, and still more preferably greater than 0.78. The value of the right-hand side of formula (1) is preferably 0.0202, more preferably 0.0195, even more preferably 0.0190, even more preferably 0.0187, and still more preferably 0.0181. There is no particular upper limit, but it is usually around 0.850.

[0071] The value of μ can be adjusted by conventional methods in the tire industry. Specifically, it can be adjusted by changing the type and amount of chemicals (e.g., rubber components, fillers, resin components, oils, sulfur, vulcanization accelerators, silane coupling agents, etc.) blended into the rubber composition that makes up the tread. For example, increasing the content of the resin component that exhibits tackiness can increase the value of μ, while decreasing it can decrease the value of μ.

[0072] (Circumferential groove, land area) Preferably, the tread surface of the tread has one or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land areas partitioned by the circumferential grooves.

[0073] The circumferential grooves may extend in a straight line or in a zigzag pattern. Furthermore, while there may be one or more circumferential grooves, having two or more divides the tread into at least one pair of shoulder tread sections and a center tread section sandwiched between them. Having three or more circumferential grooves further divides the center tread into a section that faces the inside of the vehicle and a section that faces the outside when mounted on the vehicle. This allows for different tread patterns in each section, which is preferable as it increases the design flexibility of the tread pattern. The number of circumferential grooves may be four or more, or even five or more.

[0074] The ratio of the area of ​​the circumferential grooves to the area of ​​the tread contact surface is preferably more than 19% and less than 32%. More preferably this ratio is 20% or more, and even more preferably 22% or more. On the other hand, the ratio is more preferably 30% or less, and even more preferably 28% or less.

[0075] When there are three or more circumferential grooves, the circumferential grooves consist of a pair of outermost circumferential grooves at the outermost edges in the tire width direction, and a center circumferential groove located inward in the tire width direction from the pair of outermost circumferential grooves. For example, Figure 3 shows three circumferential grooves: a center circumferential groove 11 and outermost circumferential grooves 12 and 13. In this case, the land area is divided into a shoulder land area located outward in the tire width direction from the outermost circumferential grooves, and a center land area located inward in the tire width direction from the outermost circumferential grooves. For example, Figure 3 shows center land areas 21 and 22 and shoulder land areas 23 and 24. The groove width of the center circumferential groove is preferably wider than that of the outermost circumferential groove. This is because it improves the drainage performance in the center of the tire and can contribute to improved grip performance. For example, in Figure 3, the groove width of the center circumferential groove 11 is wider than that of the outermost circumferential grooves 12 and 13.

[0076] (Yokomizo) Preferably, the aforementioned land portion has transverse grooves extending in the tire width direction.

[0077] The width of the lateral groove is not particularly limited, but is usually 8 mm or less. Also, grooves with a width of less than 2 mm are sometimes distinguished from grooves as sipes, but the lateral grooves of the present invention also include grooves with a width of less than 2 mm. The direction of the lateral groove may be at a predetermined angle with respect to the tire width direction. The range of this angle is, for example, 0° to ±80°. The angle of a single lateral groove may be constant at any position in the tire width direction, or the angle may change according to the displacement of the position in the tire width direction. At least one end of the lateral groove may communicate with the circumferential groove or the tread contact edge, or both ends may communicate with the circumferential groove or the tread contact edge, or neither end may communicate.

[0078] Preferably, the aforementioned lateral groove has a portion (widened portion) in a cross section perpendicular to the tire diameter where the groove width is wider than the groove width on the tread surface. The shape of the widened portion is not particularly limited, as long as the drainage performance improves as the tire wears, and this can improve grip performance. For example, Figure 3 shows widened lateral grooves 31 and 32, which have a widened portion. In such widened lateral grooves, the groove width is uniformly widened along the tire diameter from the tread surface to the bottom of the groove, that is, the widest groove width is at the bottom of the groove. Therefore, the drainage performance improves as the tire wears down.

[0079] Preferably, the shoulder portion has a shoulder lateral groove extending in the tire width direction, and the center portion has a center lateral groove extending in the tire width direction. In this case, it is preferable that one end of the shoulder lateral groove opens to the tread contact edge and the other end opens to the outermost circumferential groove, and one end of the center lateral groove opens to the outermost circumferential groove and the other end opens to the center circumferential groove, and further, that the shoulder lateral groove and the center lateral groove constitute a series of lateral grooves that extend continuously from the tread contact edge toward the tire equatorial plane. For example, Figure 3 shows center portion 21, 22 and the center lateral grooves 35, 36 that they each have, and also shows shoulder portion 23, 24 and the shoulder lateral grooves 37, 38 that they each have. Furthermore, the shoulder lateral grooves 37 and 38 each have one end opening to the tread contact edge Te and the other end opening to the outermost circumferential grooves 12 and 13, while the center lateral grooves 35 and 36 each have one end opening to the outermost circumferential grooves 12 and 13 and the other end opening to the center circumferential groove 11. In addition, the shoulder lateral grooves 37 and 38 and the center lateral grooves 35 and 36 each constitute a series of lateral grooves that extend continuously from the tread contact edge toward the tire equator.

[0080] [Rubber composition] The rubber composition constituting the tread according to the present invention will be described below.

[0081] <Rubber components> The rubber component in the rubber composition preferably includes isoprene rubber, and more preferably includes isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR). Alternatively, the rubber component may consist solely of isoprene rubber, SBR, and BR.

[0082] (Isoprene rubber) Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, examples include SIR20, RSS#3, TSR20, etc., which are commonly used in the tire industry. For IR, there are no particular limitations; examples include IR2200, etc., which are commonly used in the tire industry. Examples of modified NRs include deproteinized natural rubber (DPNR) and high-purity natural rubber. Examples of modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. Isoprene-based rubbers may be used individually or in combination of two or more types.

[0083] When an isoprene-based compound is included, its content in 100% by mass of the rubber component is preferably more than 20% by mass, more preferably more than 25% by mass, even more preferably more than 30% by mass, and particularly preferably more than 35% by mass, from the viewpoint of processability and durability. On the other hand, there is no particular upper limit to the content of isoprene-based compound in the rubber component, but it is preferably less than 85% by mass, more preferably less than 80% by mass, even more preferably less than 75% by mass, and particularly preferably less than 70% by mass.

[0084] (SBR) SBR is not particularly limited and can be any solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), or modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, branched structures, etc.). Furthermore, hydrogenated SBRs (hydrogenated SBRs) can also be used. Among these, S-SBR is preferred, and modified S-SBR is more preferred. SBR may be used alone or in combination of two or more types.

[0085] Modified SBRs include modified SBRs into which functional groups commonly used in this field have been introduced. Examples of these functional groups include amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), amide groups, silyl groups, alkoxysilyl groups (preferably alkoxysilyl groups with C1-C6), isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups (preferably alkoxy groups with C1-C6), hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may also have substituents. Examples of substituents include functional groups such as amino groups, amide groups, alkoxysilyl groups, carboxyl groups, and hydroxyl groups. Furthermore, modified SBRs include hydrogenated, epoxidized, and tin-modified SBRs.

[0086] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0087] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., and ZS Elastomer Co., Ltd. can be used.

[0088] The styrene content of SBR is preferably more than 15% by mass, more preferably more than 20% by mass, and even more preferably more than 25% by mass, from the viewpoint of ensuring damping properties in the tread and wet grip performance. Furthermore, from the viewpoint of the temperature dependence of grip performance and wear resistance, it is preferably less than 60% by mass, more preferably less than 50% by mass, and even more preferably less than 40% by mass. The styrene content of SBR is measured by the method described above.

[0089] The vinyl bonding amount of SBR is preferably more than 10 mol%, more preferably more than 20 mol%, and even more preferably more than 30 mol%, from the viewpoint of ensuring reactivity with silica, rubber strength, and abrasion resistance. Furthermore, from the viewpoint of preventing increased temperature dependence, wet grip performance, elongation at break, and abrasion resistance, the vinyl bonding amount of SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and even more preferably less than 60 mol%. The vinyl bonding amount of SBR (amount of 1,2-bonded butadiene units) is measured by the method described above.

[0090] The weight-average molecular weight (Mw) of SBR is preferably over 150,000, more preferably over 200,000, and even more preferably 250,000 or more, from the viewpoint of wear resistance. Furthermore, from the viewpoint of crosslinking uniformity, Mw is preferably less than 2,500,000, more preferably less than 2,000,000, and even more preferably less than 1,000,000. Mw can be determined by the method described above.

[0091] When SBR is included, the content of SBR in 100% by mass of the rubber component is preferably more than 10% by mass, more preferably more than 20% by mass, even more preferably more than 30% by mass, and particularly preferably more than 40% by mass, from the viewpoint of ensuring damping properties in the tread and wet grip performance. Furthermore, from the viewpoint of improving durability by suppressing heat generation in the tread, it is preferably less than 85% by mass, more preferably less than 80% by mass, even more preferably less than 75% by mass, and particularly preferably less than 70% by mass.

[0092] (BR) The type of BR is not particularly limited, and common types used in the tire industry can be used, such as BR with a cis content (amount of cis-1,4-bonded butadiene units) exceeding 90 mol% (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). Modified BR can be BR modified with functional groups similar to those described for SBR above. BR may be used alone or in combination of two or more types.

[0093] Examples of high-cis BR include those manufactured by Nippon Zeon Co., Ltd., Ube Industries, Ltd., and JSR Corporation. Including high-cis BR can improve low-temperature properties and wear resistance. The cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. A cis content of 98 mol% or more is also preferable. The cis content is a value calculated by the method described above.

[0094] Rare earth-based BR is synthesized using a rare earth element catalyst, and the vinyl bond content (amount of 1,2-linked butadiene units) is preferably less than 1.8 mol%, more preferably less than 1.0 mol%, and even more preferably less than 0.8 mol%, and the cis content (amount of cis-1,4-linked butadiene units) is preferably greater than 95 mol%, more preferably greater than 96 mol%, and even more preferably 97 mol% or more. As rare earth-based BR, for example, those manufactured by Lanxess K.K. can be used.

[0095] SPB-containing BR refers to BR in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to and dispersed in BR. Examples of such SPB-containing BR include those manufactured by Ube Industries, Ltd.

[0096] As the modified BR, a modified butadiene rubber (modified BR) is preferably used in which the terminal and / or main chain is modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0097] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the ends of the modified BR molecule are linked by a tin-carbon bond (tin-modified BR). Furthermore, the modified BR may be either unhydrogenated or hydrogenated.

[0098] From the viewpoint of preventing low-temperature brittleness, the glass transition temperature (Tg) of BR is preferably less than -14°C, more preferably less than -17°C, and even more preferably less than -20°C. On the other hand, there is no particular lower limit to the Tg, but from the viewpoint of wear resistance, it is preferably above -150°C, more preferably above -120°C, and even more preferably above -110°C. The glass transition temperature is the value measured by the method described above.

[0099] From the viewpoint of wear resistance, the weight-average molecular weight (Mw) of BR is preferably over 300,000, more preferably over 350,000, and even more preferably over 400,000. From the viewpoint of crosslinking uniformity, it is preferably less than 2,000,000, more preferably less than 1,500,000, and even more preferably less than 1,000,000. Mw can be determined by the method described above.

[0100] When BR is included, the content of BR in 100% by mass of the rubber component is preferably more than 1% by mass, more preferably more than 5% by mass, and even more preferably 10% by mass or more, from the viewpoint of wear resistance performance. Furthermore, from the viewpoint of wet grip performance, it is preferably less than 40% by mass, more preferably less than 35% by mass, even more preferably less than 30% by mass, and particularly preferably less than 25% by mass.

[0101] (Other rubber components) The rubber component according to the present invention may include rubber components other than the isoprene-based rubber, SBR, and BR mentioned above. Other rubber components that can be crosslinked are commonly used in the tire industry. Examples include diene-based rubbers such as styrene-isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), and non-diene-based rubbers such as ethylene-propylene diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). These other rubber components may be used individually or in combination of two or more.

[0102] <Filler> The rubber composition according to the present invention preferably contains a filler. The filler preferably contains carbon black and silica. Further, the filler may be a filler consisting only of carbon black and silica.

[0103] (Carbon Black) Carbon black is not particularly limited, and those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991 and the like can be suitably used, and in-house synthesized products and the like can also be suitably used in addition to the above. These carbon blacks may be used alone, or two or more of them may be used in combination.

[0104] The nitrogen adsorption specific surface area (N2SA) of carbon black, from the viewpoints of weather resistance and reinforcing property, is 50 m 2 / g is preferably more than 2 / g is more preferably more than 80 m 2 / g is even more preferably more than 100 m 2 / g is preferably less than 250 m 2 / g is more preferably less than 220 m 2 / g is even more preferably less than 200 m

[0105] When carbon black is included, the content per 100 parts by mass of rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass, from the viewpoint of weather resistance and reinforcing properties. Furthermore, from the viewpoint of improving durability by suppressing heat generation in the tread area, it is preferably less than 40 parts by mass, more preferably less than 30 parts by mass, and even more preferably less than 20 parts by mass.

[0106] (silica) The silica used is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by the dry method (anhydrous silica) or silica prepared by the wet method (hydrated silica). Among these, hydrated silica prepared by the wet method is preferred because it contains a large number of silanol groups. Silica may be used alone or in combination of two or more types.

[0107] The specific surface area (N2SA) of silica for nitrogen adsorption is 140m², from the viewpoint of ensuring reinforcement and damping in the tread area. 2 Preferably more than / g, 150m 2 More preferably 160m / g or more, 2 More preferably than / g, 170m 2 A value exceeding / g is particularly preferred. Furthermore, from the viewpoint of heat generation and processability, 350m 2 Preferably less than / g, 300m 2 Less than / g is more preferable, 250m 2 A value less than / g is even more preferable. Note that the N2SA of silica is the value measured by the method described above.

[0108] The average primary particle diameter of silica is preferably less than 20 nm, more preferably less than 19 nm, and even more preferably less than 18 nm. The lower limit of the average primary particle diameter is not particularly limited, but is preferably greater than 1 nm, more preferably greater than 3 nm, and even more preferably greater than 5 nm. By having the average primary particle diameter of silica within the above range, the dispersibility of silica can be further improved, and the reinforcing properties, fracture properties, and wear resistance can be further improved. The average primary particle diameter of silica can be determined by the method described above.

[0109] When silica is included, the silica content per 100 parts by mass of rubber component is preferably more than 20 parts by mass, more preferably more than 25 parts by mass, even more preferably more than 30 parts by mass, and particularly preferably more than 35 parts by mass, from the viewpoint of ensuring damping properties in the tread and wet grip performance. Furthermore, from the viewpoint of reducing the specific gravity of the rubber and achieving weight reduction, as well as from the viewpoint of improving durability by suppressing heat generation in the tread and ensuring ride comfort performance through the softness of the rubber, it is preferably less than 80 parts by mass, more preferably less than 75 parts by mass, even more preferably less than 70 parts by mass, and particularly preferably less than 65 parts by mass.

[0110] (Mass ratio of silica to carbon black) The mass ratio of silica to carbon black is preferably greater than 1.0, more preferably greater than 2.0, even more preferably greater than 3.0, and particularly preferably 4.0 or more. The upper limit of this mass ratio is not particularly limited, but is preferably less than 15.0, more preferably less than 10.0, even more preferably less than 8.0, and particularly preferably less than 6.0.

[0111] (Other fillers) Other fillers besides silica and carbon black can include aluminum hydroxide, calcium carbonate, alumina, clay, talc, and other materials commonly used in the tire industry.

[0112] (Total content of fillers) The total content of the filler relative to 100 parts by mass of rubber component is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, even more preferably less than 100 parts by mass, and particularly preferably less than 80 parts by mass, from the viewpoint of suppressing the complex modulus of elasticity (30°C E*) (MPa) at 30°C and suppressing damage due to heat generation. Furthermore, from the viewpoint of ensuring reinforcing properties and damping properties in the tread portion, it is preferably more than 20 parts by mass, more preferably more than 25 parts by mass, even more preferably more than 30 parts by mass, and particularly preferably more than 35 parts by mass.

[0113] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used, for example, the following mercapto-type silane coupling agents; sulfide-type silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; thioester-type silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; vinyltri Examples include vinyl silane coupling agents such as methoxysilane; amino silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. In particular, it is preferable to contain a sulfide silane coupling agent and / or a mercapto silane coupling agent. These silane coupling agents may be used individually or in combination of two or more.

[0114] The mercapto-silane coupling agent is preferably a compound represented by the following chemical formula (1), and / or a compound containing a bonding unit A represented by the following chemical formula (2) and a bonding unit B represented by the following chemical formula (3). [ka] (In the formula, R 101 , R 102 , and R 103 Each of these is independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R111 -O) z -R 112 (z R 111 Each of these independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 R represents an alkyl group with 1 to 30 carbon atoms, an alkenyl group with 2 to 30 carbon atoms, an aryl group with 6 to 30 carbon atoms, or an aralkyl group with 7 to 30 carbon atoms; z represents an integer from 1 to 30. 104 (This represents alkylenes with 1 to 6 carbon atoms.) [ka] [ka] (In the formula, x represents an integer greater than or equal to 0; y represents an integer greater than or equal to 1; R 201 R represents a hydrogen atom, or an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms, which may be substituted with a halogen atom, hydroxyl, or carboxyl; 202 R represents alkylene with 1 to 30 carbon atoms, alkenylene with 2 to 30 carbon atoms, or alkynylene with 2 to 30 carbon atoms; where R 201 and R 202 (They may form a ring structure.)

[0115] Examples of compounds represented by chemical formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following chemical formula (4) (Si363 manufactured by Evonik Degussa). The compound represented by the following chemical formula (4) can be preferably used. These may be used individually or in combination of two or more. [ka]

[0116] Examples of compounds containing the bonding unit A shown in chemical formula (2) and the bonding unit B shown in chemical formula (3) include NXT-Z30, NXT-Z45, NXT-Z60, and NXT-Z100 manufactured by Momentive. These may be used individually or in combination of two or more.

[0117] When a silane coupling agent is included, the content per 100 parts by mass of silica is preferably more than 1.0 part by mass, more preferably more than 3.0 parts by mass, and even more preferably more than 5.0 parts by mass, from the viewpoint of improving silica dispersibility. Furthermore, from the viewpoint of preventing a decrease in wear resistance, it is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 15 parts by mass.

[0118] <Resin components> The rubber composition according to the present invention preferably contains a resin component.

[0119] The resin components are not particularly limited, but examples include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry. The resin components may be used individually or in combination of two or more.

[0120] Examples of petroleum resins include C5-based petroleum resins, aromatic petroleum resins, and C5C9-based petroleum resins. Petroleum resins may be used individually or in combination of two or more types.

[0121] "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5 petroleum resin. "Aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, and these may be hydrogenated or modified resins. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins include coumarone indene resin, coumarone resin, indene resin, and aromatic vinyl resins, which are preferably used. As aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, for reasons of being economical, easy to process, and having excellent heat generation properties. As aromatic vinyl resins, commercially available products from companies such as Kraton and Eastman Chemical can be used. "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and these may be hydrogenated or modified. The C5 fraction and C9 fraction are the petroleum fractions mentioned above. As C5C9 petroleum resins, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0122] Examples of terpene resins include polyterpene resins consisting of at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc.; aromatically modified terpene resins made from the terpene compound and an aromatic compound; terpene-phenol resins made from the terpene compound and a phenolic compound; and hydrogenated terpene resins obtained by hydrogenating these terpene resins. Examples of aromatic compounds used as raw materials for aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds used as raw materials for terpene-phenol resins include phenol, bisphenol A, cresol, and xylenol. Terpene resins may be used individually or in combination of two or more types.

[0123] The rosin resin is not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc. The rosin resin may be used alone or in combination of two or more types.

[0124] Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin. Phenolic resins may be used individually or in combination of two or more types.

[0125] As for the resin component, from the viewpoint of increasing the static friction coefficient, it is preferable to include at least one selected from the group consisting of C5C9 petroleum resin, terpene resin, and rosin resin.

[0126] From the viewpoint of wet grip performance, the softening point of the resin component is preferably above 60°C, more preferably above 65°C, and even more preferably above 70°C. Furthermore, from the viewpoint of processability and improved dispersibility between the rubber component and filler, it is preferably below 150°C, more preferably below 140°C, and even more preferably below 130°C. The softening point is measured by the method described above.

[0127] When a resin component is included, the content of the rubber component per 100 parts by mass is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, even more preferably more than 15 parts by mass, and particularly preferably 20 parts by mass or more, from the viewpoint of grip performance. Furthermore, from the viewpoint of durability performance, it is preferably 60 parts by mass or less, more preferably less than 50 parts by mass, even more preferably less than 40 parts by mass, and particularly preferably 20 parts by mass or less.

[0128] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to the present invention may appropriately contain compounding agents commonly used in the tire industry, such as oils, waxes, processing aids, zinc oxide, stearic acid, antioxidants, sulfur, and other vulcanizing agents and accelerators.

[0129] (oil) Examples of oils include process oils, vegetable oils, and animal fats. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Furthermore, for environmental reasons, process oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA process oils include light extraction solvates (MES), processed distillate aromatic extracts (TDAEs), and heavy naphthenic oils. Additionally, from a life cycle assessment perspective, refined waste oil from rubber mixers and engines, or waste cooking oil used in restaurants, may be used. Oils may be used individually or in combination of two or more types.

[0130] When oil is included, the oil content per 100 parts by mass of rubber component is preferably more than 1 part by mass, more preferably more than 2 parts by mass, and even more preferably more than 3 parts by mass, from the viewpoint of processability. Furthermore, from the viewpoint of low fuel consumption and durability, it is preferably less than 80 parts by mass, more preferably less than 60 parts by mass, and even more preferably less than 40 parts by mass. Note that the oil content also includes the amount of oil contained in the oil-spread rubber.

[0131] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as petroleum-based waxes, mineral-based waxes, and synthetic waxes. Among these, petroleum-based waxes are preferred. Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. Waxes that can be used include those manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. Waxes can be used individually or in combination of two or more types.

[0132] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably less than 10 parts by mass, more preferably less than 8 parts by mass, and even more preferably less than 5 parts by mass.

[0133] (Processing aid) As processing aids, fatty acid metal salts can be used to lower the viscosity of the rubber and ensure mold release properties before vulcanization, and commercially available compatibilizers can be used to suppress microscopic layer separation of rubber components.

[0134] When processing aids are included, the content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass, from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably less than 10 parts by mass, more preferably less than 8 parts by mass, and even more preferably less than 5 parts by mass.

[0135] (Anti-aging agent) The anti-aging agent is not particularly limited, but examples include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts. Phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. The anti-aging agent may be used alone or in combination of two or more types.

[0136] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass.

[0137] (Zinc oxide) When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass.

[0138] (Stearic acid) When stearic acid is included, its content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass.

[0139] (Vulcanizing agent) Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0140] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably more than 0.1 parts by mass, more preferably more than 0.3 parts by mass, and even more preferably more than 0.5 parts by mass, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 3.0 parts by mass. When oil-containing sulfur is used as the vulcanizing agent, the amount of vulcanizing agent shall be the total amount of pure sulfur contained in the oil-containing sulfur.

[0141] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These non-sulfur vulcanizing agents can be purchased commercially from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0142] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, but examples include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Among these, sulfenamide and guanidine vulcanization accelerators are preferred because they more favorably provide the desired effect. The vulcanization accelerator may be used alone or in combination of two or more types.

[0143] Examples of sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-oxyethylene-2-benzothiazolyl sulfenamide, N,N'-diisopropyl-2-benzothiazolyl sulfenamide, and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide. Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazolyl disulfide. Examples of guanidine-based vulcanization accelerators include diphenylguanidine (DPG), diortotolylguanidine, and orthotolylbiguanidine.

[0144] When a vulcanization accelerator is included, its content per 100 parts by mass of rubber component is preferably more than 1.0 part by mass, more preferably more than 1.5 parts by mass, and even more preferably more than 2.0 parts by mass. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of rubber component is preferably less than 8.0 parts by mass, more preferably less than 7.0 parts by mass, even more preferably less than 6.0 parts by mass, and particularly preferably less than 5.0 parts by mass. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0145] [Manufacturing] A tire having a tread made of a predetermined rubber composition according to the present invention can be manufactured by known methods.

[0146] The rubber composition can be manufactured by known methods, for example, by mixing each of the components using a rubber mixing device such as an open roll or closed-type kneader (Banbury mixer, kneader, etc.).

[0147] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired.

[0148] There are no particular limitations on the mixing conditions, but for example, in the base mixing process, mixing is performed at a discharge temperature of 150-170°C for 3-10 minutes, and in the final mixing process, mixing is performed at 70-110°C for 1-5 minutes. There are no particular limitations on the vulcanization conditions, but for example, vulcanization is performed at 150-200°C for 10-30 minutes.

[0149] The tire of the present invention can be manufactured by conventional methods. Specifically, the unvulcanized rubber composition is extruded in an extruder equipped with a die of a predetermined shape to match the shape of the tread, bonded together with other tire components on a tire molding machine, and molded in a conventional manner to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to manufacture the tire. The vulcanization conditions are not particularly limited, and for example, a method of vulcanization at 150 to 200°C for 10 to 30 minutes can be used.

[0150] [Application] Tires include pneumatic tires and non-pneumatic tires. Of these, pneumatic tires are preferred. The tires can be used for passenger cars, large passenger cars, large SUVs, heavy-duty trucks and buses, light trucks, motorcycles, and racing tires (high-performance tires). Among these, they are particularly suitable for use in passenger cars. [Examples]

[0151] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

[0152] We examined tires having treads made of rubber compositions obtained according to the table below using the various chemicals listed below, and the results calculated based on the analysis and evaluation methods described below are shown in Tables 1 to 3.

[0153] NR:TSR20 SBR: Modified solution polymerized SBR produced in Production Example 1 described below (styrene content: 30% by mass, vinyl bond content: 52 mol%, Mw: 250,000, non-oil product) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97 mol%, Tg: -108℃, Mw: 440,000) Carbon Black: Mitsubishi Chemical Corporation's Dia Black N220 (N2SA: 115ml) 2 / g) Silica: ULTRASIL(registered trademark) VN3 (N2SA: 175m) manufactured by Evonik Degussa. 2 / g, average primary particle diameter: 17nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa. Oil: H&R VivaTec400 (TDAE oil) Resin component 1: PetroTac 100V manufactured by Tosoh Corporation (C5C9 petroleum resin, copolymer of C5 and C9 fractions, softening point: 96°C) Resin component 2: YS Resin PX1150 manufactured by Yasuhara Chemical Co., Ltd. (terpene-based resin, polyterpene (β-pinene resin), softening point 115℃) Resin component 3: Harima Chemicals Co., Ltd.'s Harima T-80 (rosin-based resin, maleic acid-modified rosin resin, softening point: 85°C) Resin component 4: Sylvares SA85 manufactured by Kraton (aromatic vinyl resin, copolymer of α-methylstyrene and styrene, softening point: 85°C) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Anti-aging agent: Nocrack 6C (N-phenyl-N'-( 1,3-dimethylbutyl)-p-phenylenediamine) Wax: OZ0355 manufactured by Nippon Seiro Co., Ltd. Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0154] Manufacturing Example 1: Synthesis of SBR Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to initiate polymerization. Polymerization proceeds under adiabatic conditions, reaching a maximum temperature of 85°C. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and polymerization is continued for another 5 minutes. Then, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane is added as a modifier to carry out the reaction. After the polymerization reaction is complete, 2,6-di-tert-butyl-p-cresol is added. Subsequently, the solvent is removed by steam stripping, and the mixture is dried on a heated roller at 110°C to obtain SBR.

[0155] <Examples and Comparative Examples> According to the formulations shown in each table, the chemicals other than sulfur and vulcanization accelerator are mixed in a 1.7 L sealed Banbury mixer for 1 to 10 minutes until the discharge temperature reaches 150 to 160°C to obtain a mixture. Next, using a twin-screw open roll mixer, sulfur and vulcanization accelerator are added to the obtained mixture and mixed for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is press-vulcanized at 170°C for 12 minutes to produce a test rubber composition.

[0156] Unvulcanized rubber compositions with the formulations shown in Tables 1 to 3 were extruded using an extruder equipped with a tread-shaped die, and bonded together with tire components other than the tread to form an unvulcanized tire. These were then press-vulcanized at 170°C for 12 minutes to produce and prepare three test tires: Test Tire 1 (size: 195 / 65R15 91V, rim: 15×6.0J), Test Tire 2 (size: 215 / 55R18 95T, rim: 18×7.0J), and Test Tire 3 (size: 215 / 60R16 99V, rim: 16×6.5J).

[0157] The obtained test rubber compositions and test tires were evaluated as follows. The evaluation results are shown in Tables 1 to 3. The maximum load capacity WL (kg) for each tire was calculated using formulas (1) and (2) above, based on the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm) of each tire measured under normal conditions.

[0158] <30°C tanδ, 0°C tanδ, and 30°C E*> From the inside of the tread of each test tire, a sample measuring 20 mm in length, 4 mm in width, and 1 mm in thickness is cut out so that the longer side is in the circumferential direction of the tire and the thickness is in the radial direction of the tire, and this is used as a rubber test piece.

[0159] For each rubber test specimen, tanδ was measured using a GABO iplexer series under the following conditions: temperature 0°C, initial strain 10%, dynamic strain 2.5%, and frequency 10Hz, and under the following conditions: temperature 30°C, initial strain 5%, dynamic strain 1%, and frequency 10Hz.

[0160] Furthermore, the complex modulus (E*) (MPa) of each rubber test piece is measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz.

[0161] <Static friction coefficient μ> From the surface of the tread of each test tire, a sample measuring 27 mm in length, 25 mm in width, and 8 mm in thickness is cut out so that the longer side is in the circumferential direction of the tire and the thickness is in the radial direction of the tire, and this is used as a rubber test piece.

[0162] For each rubber test piece, the static friction coefficient is measured using a TL501 SLIPMETER (manufactured by Trinity Lab Co., Ltd.) on a road surface conforming to ISO 15222, under conditions of a contact pressure of 0.30 MPa and a measurement temperature of 25°C, by pushing the piece down from θ=0° (vertical position) to 60° at a constant speed over 3 seconds. The static friction coefficient is measured five times using the same method, and the average value is defined as μ.

[0163] <Dry grip performance> Each test tire is mounted on all wheels of a vehicle (domestic FF 2000cc), and the braking distance from the point of braking at a speed of 100 km / h is measured on a dry asphalt surface. The braking distance of the control tire (reference comparison) is set to 100, and the reciprocal of the braking distance of each test tire is expressed as an index using the following formula. A higher index indicates better dry grip performance. (Dry grip performance index) = (Braking distance of the control tire) / (Braking distance of each test tire)

[0164] [Table 1]

[0165] [Table 2]

[0166] [Table 3]

[0167] <Embodiment> Preferred embodiments are shown below.

[0168] [1] A tire having a tread, The tread is made of a rubber composition containing rubber components, The ratio of the tire weight G (kg) to the tire's maximum load capacity WL (kg) (G / WL) is 0.0150 or less, preferably 0.0145 or less. A tire in which G / WL and μ satisfy the following equation (1), when the average value of the static friction coefficient of the rubber composition measured five times on a road surface conforming to ISO 15222 at a ground pressure of 0.30 MPa and a measurement temperature of 25°C is μ. (G / WL) / μ≦0.0214 (1) [2] The tire according to [1] above, wherein the G / WL value is 0.0140 or less, preferably less than 0.0140, more preferably less than 0.0135, and even more preferably 0.0131 or less. [3] The tire according to [1] or [2] above, wherein the value of μ is 0.65 or greater, preferably 0.70 or greater, more preferably greater than 0.75, and even more preferably greater than 0.78. [4] The tire according to any one of the above [1] to [3], wherein the value of the right-hand side of formula (1) is 0.0202, preferably 0.0195, more preferably 0.0190, even more preferably 0.0187, and even more preferably 0.0181. [5] The tire according to any one of the above items [1] to [4], wherein the rubber component includes isoprene rubber. [6] The tire according to any one of the above [1] to [5], wherein the rubber composition comprises a resin component. [7] The tire according to any one of the above [1] to [6], wherein the loss loss tangent (30°C tanδ) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, is greater than 0.17, preferably greater than 0.20, more preferably 0.21 or higher, even more preferably 0.22 or higher, even more preferably 0.23 or higher, and even more preferably 0.24 or higher. [8] The tire according to any one of the above [1] to [7], wherein the complex modulus of elasticity (30°CE*) (MPa) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, is less than 9.5, preferably less than 9.0, more preferably 8.9 or less, even more preferably less than 8.5, even more preferably less than 8.4, even more preferably 8.3 or less, even more preferably 8.2 or less, and even more preferably 8.1 or less. [9] The tire according to any one of the above [1] to [8], wherein the product of the loss tangent (30°C tanδ) of the rubber composition measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, and the loss tangent (0°C tanδ) of the rubber composition measured under conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, and a frequency of 10Hz, is greater than 0.11, preferably 0.12 or more, more preferably 0.13 or more, and even more preferably 0.15 or more.

[10] The rubber composition contains a resin component, The tire according to any one of the above [1] to [9], wherein the content of the resin component is more than 10 parts by mass, preferably more than 15 parts by mass, and more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component.

[11] The rubber composition comprises a resin component, The tire according to any one of the above [1] to

[10] , wherein the resin component comprises at least one selected from the group consisting of C5C9 petroleum resin, terpene resin, and rosin resin.

[12] The rubber composition comprises a filler, The filler comprises carbon black and silica, The tire according to any one of the above [1] to

[11] , wherein the mass ratio of the silica to the carbon black is greater than 1.0, preferably greater than 2.0, more preferably greater than 3.0, and even more preferably 4.0 or more.

[13] The tread surface of the tread has one or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land portions partitioned by the circumferential grooves, The aforementioned land portion has transverse grooves extending in the tire width direction, The tire according to any one of the above [1] to

[12] , wherein the lateral groove has a portion in a cross section perpendicular to the tire diameter in which the groove width is wider than the groove width on the tread surface.

[14] The tread surface of the tread has one or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land portions partitioned by the circumferential grooves, The tire according to any one of the above [1] to

[13] , wherein the ratio of the area of ​​the circumferential grooves to the area of ​​the tread contact surface is more than 19% and less than 32%, preferably 20% or more and 30%, and more preferably 22% or more and 28%.

[15] The tread surface of the tread has three or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land portions partitioned by the circumferential grooves, The aforementioned circumferential groove consists of a pair of outermost circumferential grooves in the tire width direction and a center circumferential groove located inward from the pair of outermost circumferential grooves in the tire width direction. The aforementioned land portion is divided into a shoulder land portion located outside the outermost circumferential groove in the tire width direction, and a center land portion located inside the outermost circumferential groove in the tire width direction. The shoulder portion has a shoulder lateral groove extending in the tire width direction, and the center portion has a center lateral groove extending in the tire width direction. The aforementioned shoulder lateral groove has one end that opens to the tread contact edge and the other end that opens to the outermost circumferential groove. The aforementioned center lateral groove has one end opening into the outermost groove and the other end opening into the center circumferential groove. The tire according to any one of the above [1] to

[14] , wherein the shoulder lateral groove and the center lateral groove constitute a series of lateral grooves that extend continuously from the tread contact edge toward the tire equator. [Explanation of Symbols]

[0169] Wt... Tire section width Ht... Tire section height Dt... Tire outer diameter 11. Center circumferential groove 12. Outermost directional grooves 13. Outermost directional groove 21. Center Track and Field Club 22. Center Track and Field Club 23. Shoulder Track and Field Club 24 ··Shoulder Track and Field Club 31. Widening of lateral grooves 32. Widening of lateral grooves 33. Widening of lateral grooves 34. Widening of lateral grooves 35. Center horizontal groove 36. Center horizontal groove 37. Shoulder strap with horizontal grooves. 38. Shoulder strap with horizontal grooves. Te··Tread contact point EP...Tire equatorial plane

Claims

1. A tire having a tread, The tread is made of a rubber composition containing rubber components, The ratio of the tire weight G (kg) to the tire's maximum load capacity WL (kg) (G / WL) is 0.0150 or less. A tire in which G / WL and μ satisfy the following equation (1), when the average value of the static friction coefficient of the rubber composition measured five times on a road surface conforming to ISO 15222 at a ground pressure of 0.30 MPa and a measurement temperature of 25°C is μ. (G / WL) / μ≦0.0214 (1)

2. The tire according to claim 1, wherein the G / WL value is 0.0140 or less.

3. The tire according to claim 1 or 2, wherein the value of μ is 0.65 or greater.

4. The tire according to claim 1 or 2, wherein the value of the right-hand side of formula (1) is 0.0202.

5. The tire according to claim 1 or 2, wherein the rubber component includes isoprene-based rubber.

6. The tire according to claim 1 or 2, wherein the rubber composition comprises a resin component.

7. The tire according to claim 1 or 2, wherein the loss tangent (30°C tanδ) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, is greater than 0.

17.

8. The tire according to claim 1 or 2, wherein the complex modulus of elasticity (30°C E*) (MPa) of the rubber composition, measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10 Hz, is less than 9.

5.

9. The tire according to claim 1 or 2, wherein the product of the loss tangent (30°C tanδ) of the rubber composition measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10Hz, and the loss tangent (0°C tanδ) of the rubber composition measured under conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, and a frequency of 10Hz, is greater than 0.

11.

10. The rubber composition contains a resin component, The tire according to claim 1 or 2, wherein the content of the resin component is more than 10 parts by mass per 100 parts by mass of the rubber component.

11. The rubber composition contains a resin component, The tire according to claim 1 or 2, wherein the resin component comprises at least one selected from the group consisting of C5C9 petroleum resin, terpene resin, and rosin resin.

12. The rubber composition comprises a filler, The filler comprises carbon black and silica, The tire according to claim 1 or 2, wherein the mass ratio of the silica to the carbon black is greater than 1.

0.

13. The tread surface of the tread has one or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land areas partitioned by the circumferential grooves, The aforementioned land portion has transverse grooves extending in the tire width direction, The tire according to claim 1 or 2, wherein the lateral groove has a portion in a cross section perpendicular to the tire's radial direction in which the groove width is wider than the groove width on the tread surface.

14. The tread surface of the tread has one or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land areas partitioned by the circumferential grooves, The tire according to claim 1 or 2, wherein the ratio of the area of ​​the circumferential grooves to the area of ​​the tread contact surface is more than 19% and less than 32%.

15. The tread surface of the tread has three or more circumferential grooves that extend continuously in the circumferential direction of the tire, and land areas partitioned by the circumferential grooves. The aforementioned circumferential groove consists of a pair of outermost circumferential grooves in the tire width direction and a center circumferential groove located inward from the pair of outermost circumferential grooves in the tire width direction. The aforementioned land portion is divided into a shoulder land portion located outside the outermost circumferential groove in the tire width direction, and a center land portion located inside the outermost circumferential groove in the tire width direction. The shoulder portion has a shoulder lateral groove extending in the tire width direction, and the center portion has a center lateral groove extending in the tire width direction. The aforementioned shoulder lateral groove has one end that opens to the tread contact edge and the other end that opens to the outermost circumferential groove. The aforementioned center lateral groove has one end opening into the outermost groove and the other end opening into the center circumferential groove. The tire according to claim 1 or 2, wherein the shoulder lateral groove and the center lateral groove constitute a series of lateral grooves that extend continuously from the tread contact edge toward the tire equatorial plane.

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